Eye-tracking fundus imaging system

ABSTRACT

A fundus illumination system includes an array of light sources, a first optical combiner, and a second optical combiner. The array of light sources are configured to be selectively enabled to emit non-visible light to illuminate a fundus of an eye. The first optical combiner is configured to receive reflected non-visible light that is reflected by the eye, direct a first component of the reflected non-visible light to a first camera to generate an image of the eye, and pass a second component of the reflected non-visible light. The second optical combiner is configured to receive a fundus imaging light responsive to the second component of the reflected non-visible light, and to direct the fundus imaging light to a second camera to generate an image of the fundus.

CROSS-REFERENCE TO RELATED APPLICATION

The present Application claims the benefit of U.S. ProvisionalApplication No. 62/983,339, entitled “Eye-Tracking Fundus ImagingSystem” filed Feb. 28, 2020. U.S. Provisional Application No. 62/983,339is expressly incorporated herein by reference in their entirety.

FIELD OF DISCLOSURE

Aspects of the present disclosure relate generally to ocular fundusillumination and imaging systems.

BACKGROUND

Fundus imaging involves imaging (e.g., photographing) the rear portionof the eye, also referred to as the fundus. In particular, the fundus ofthe eye is the interior surface of the eye, opposite the lens, and mayinclude the retina, optic disc, macula, fovea, and posterior pole. Insome contexts, analysis of fundus images may be useful by a careprovider for diagnostic or treatment response purposes. For example, aphysician may be able to identify issues, such as infections,degenerative eye diseases, or even congenital conditions based on theexamination of the fundus images.

Some conventional fundus imaging systems may include various optics anda flash enabled camera. The operation of these conventional imagingsystems may include directing a patient to fixate on a target image(e.g., a dot) that is projected onto the retina, and then flooding thepupil with light (e.g., activate the flash) to obtain the image.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive aspects of the present disclosure aredescribed with reference to the following figures, wherein likereference numerals refer to like parts throughout the various viewsunless otherwise specified.

FIGS. 1A and 1B illustrate a fundus imaging system, in accordance withaspects of the present disclosure.

FIG. 2A illustrates an example image of an eye captured by a firstcamera for eye-tracking, in accordance with aspects of the presentdisclosure.

FIG. 2B illustrates an example image of a fundus, captured by a secondcamera, in accordance with aspects of the present disclosure.

FIG. 3 illustrates a computing device, in accordance with aspects of thepresent disclosure.

FIG. 4 is a flow chart illustrating a process of imaging the fundus ofan eye, in accordance with aspects of the present disclosure.

FIG. 5 illustrates a head mounted display (HMD), in accordance withaspects of the present disclosure.

DETAILED DESCRIPTION

Various aspects and embodiments are disclosed in the followingdescription and related drawings to show specific examples relating to afundus imaging system that includes eye-tracking. Alternate aspects andembodiments will be apparent to those skilled in the pertinent art uponreading this disclosure and may be constructed and practiced withoutdeparting from the scope or spirit of the disclosure. Additionally,well-known elements will not be described in detail or may be omitted soas to not obscure the relevant details of the aspects and embodimentsdisclosed herein.

In some implementations of the disclosure, the term “near-eye” may bedefined as including an element that is configured to be placed within50 mm of an eye of a user while a near-eye device is being utilized.Therefore, a “near-eye optical element” or a “near-eye system” wouldinclude one or more elements configured to be placed within 50 mm of theeye of the user.

In aspects of this disclosure, visible light may be defined as having awavelength range of approximately 380 nm-700 nm. Non-visible light maybe defined as light having wavelengths that are outside the visiblelight range, such as ultraviolet light and infrared light. Infraredlight having a wavelength range of approximately 700 nm-1 mm includesnear-infrared light. In aspects of this disclosure, near-infrared lightmay be defined as having a wavelength range of approximately 700 nm-1.4μm. White light may be defined as light that includes a broad range ofwavelengths and in some instances may include multiple colors of thevisible spectrum.

As mentioned above, the operation of some conventional fundus imagingsystems may include directing a patient (or user) to fixate on a targetimage (e.g., a dot) that is projected onto their retina. One purpose ofdirecting the patient to fixate on the target image is to ensure correctalignment between the eye and the illumination source (e.g. the flash)to maximize illumination of the fundus. However, in some instances, thepatient may be unable to follow directions to fixate on the target dueto a diminished capacity, either physical or developmental. For example,a user may have eye movement issues that prevents them from focusing onthe target, or an infant/child may be unable to follow directions tofocus on the target, and so on. If the eye is misaligned with theillumination source, the pupil of the eye may vignette the illuminationlight and prevent the light from reaching the fundus, which may degradethe resultant image.

Accordingly, aspects of the present disclosure provide a fundus imagingsystem that is invariant to eye movements and/or eye alignment. That is,a fundus imaging system may maintain illumination of the fundus even ifthe eye is not directly aligned with the illumination source and/or evenas the eye moves. In one aspect, a fundus illumination source isprovided that includes an array of light sources. An eye tracker mayalso be provided that tracks movements of the eye, where one or more ofthe light sources in the array are selectively enabled to emitillumination light based on the determined movements of the eye tomaintain the illumination of the fundus while an image of the fundus isobtained. These and other features will be described in more detailbelow.

FIG. 1A illustrates a fundus imaging system 100, in accordance withaspects of the present disclosure. The fundus imaging system 100 is alsoshown as including an array of light sources 102A-102G, a layer 104, anoptical combiner 106, a lens system 108, an optical combiner 110, afirst camera 120, a computing device 122, and a second camera 126.

As shown in FIG. 1A, the light sources 102A-102G are disposed on layer104. Layer 104 may be a transparent substrate, such as glass or plastic.In one example, the light sources 102A-102G may be encapsulated withinthe transparent substrate. The transparent substrate may be transmissiveto visible light (e.g. 400 nm-750 nm) and may be configured to be placedon a display plane of an electronic or optical display layer (e.g., aliquid crystal display (LCD), an organic light emitting diode (OLED)display, a micro-LED display, a waveguide, etc.) that is configured togenerate display light for presentation to the user. In another example,layer 104 is, itself, the electronic or optical display layer, wherelight sources 102A-102G are disposed on the display layer, interspersedwithin display light that is generated by the display layer (e.g.,within the field of view of the user).

Each light source 102A-102G may be a micro light emitting diode(micro-LED), an edge emitting LED, a vertical cavity surface emittinglaser (VCSEL) diode, or a Superluminescent diode (SLED). In addition,each light source 102A-102G may be individually enabled to emitnon-visible light 107 to illuminate the eye 114. In some examples,non-visible light 107 is infrared light or near-infrared light. In someaspects, each light source 102A-102G is arranged on layer 104 in atwo-dimensional (2D) array of columns and rows. In some examples, eachlight source 102A-102G may be referred to as a point light source, whereonly one of the light sources 102A-102G are enabled at a time to emitnon-visible light 107 (e.g., in the illustrated example of FIG. 1A, onlya single light source 102D is currently enabled to emit non-visiblelight 107).

In some examples, the array of light sources 102A-102G are positioned ina plane that is conjugate to a pupil plane 116 of the eye 114. In someimplementations, the positioning of the array of light sources 102A-102Gwith respect to the eye 114 is obtained by way of a head/chinrest stand(not shown) that is provided to the user/patient. In otherimplementations, the positioning is provided by way of a head-mounteddevice (e.g., see head-mounted display of FIG. 5).

As shown in FIG. 1A, the lens system 108 is configured to receive thenon-visible light 107 and direct the non-visible light 107 to illuminatethe fundus 112 of the eye 114. In some examples, the lens system 108provides a Maxwellian view where the lens system 108 converges thenon-visible light 107 onto the pupil plane 116. As shown in FIG. 1A, thenon-visible light 107 then expands as it passes through the pupil 118towards to back of the eye 114 to illuminate a large area of the fundus112. In some aspects, the lens system 108 includes a Fresnel lens. Inother examples, the lens system 108 may include one or more otheroptical elements, such as a quarter waveplate and/or reflectivepolarizer. In some examples, the non-visible light 107 is generated bythe light sources 102A-102G to have a particular polarizationorientation. Thus, in some aspects, the lens system 108 may alter thepolarization orientation of the non-visible light 107 as it propagatesthrough the system.

FIG. 1A also illustrates fundus imaging system 100 as including anoptical combiner 106 and an optical combiner 110. Optical combiner 106is shown as being disposed between the array of light sources 102A-102Gand the optical combiner 110. In particular, optical combiner 106 may bedisposed between the array of light sources 102A-102G and the lenssystem 108. Optical combiner 110 is shown as being disposed between thearray of light sources 102A-102G and the eyeward side 103 of the fundusimaging system 100, and in particular may be disposed between the lenssystem 108 and the eyeward side 103. As will be described in more detailbelow, the optical combiner 110 may be configured to direct reflectednon-visible light (i.e., non-visible light that is reflected by the eye114) to the first camera 120 to generate images 123 of the eye 114.Similarly, optical combiner 106 may be configured to direct reflectednon-visible light to the second camera 126 to generate images 127 of thefundus 112.

In some aspects, the optical combiners 106 and 110 are transmissive tovisible light (e.g. approximately 400 nm-700 nm), such as scene light(e.g., from the environment) that is incident on the backside 105 of thefundus imaging system 100. Even still, in some examples, opticalcombiners 106 and 110 are transmissive to visible light that generatedby a display layer (e.g., layer 104). In some examples, optical combiner106 and optical combiner 110 may each be configured as a respectivepolarization-selective volume hologram (a.k.a. polarized volume hologram(PVH)) that diffracts (in reflection) a particular polarizationorientation of incident light having a particular wavelength towardcameras 126 and 120, respectively, while passing other polarizationorientations/wavelengths.

When configured as a PVH, an optical combiner may include a plurality ofliquid-crystal molecules spatially orientated to realize an opticalfunction of the PVH. In some examples, a PVH may be configured todiffract light via Bragg diffraction. In some embodiments, the Bragggrating in the PVH may be generated by adding a chiral dopant to theliquid-crystals to induce a helical twist along a light propagationdirection. The helix twist may be either left-handed or right-handedand, accordingly, the PVH may be referred to as a left-handed or aright-handed PVH. In some embodiments, the PVH may diffract circularlypolarized light having a same handedness as the helix twist of the PVHand transmit circularly polarized light having an orthogonal handedness.That is, a left-handed PVH layer may diffract a left-handed circularlypolarized (“LCP”) light and transmit a right-handed circularly polarized(“RCP”) light, while a right-handed PVH layer may diffract an RCP lightand transmit an LCP light.

The angle between the incident light and the diffracted light may dependon the wavelength of the incident light and the Bragg period of theBragg grating in the PVH. In some embodiments, depending on thealignment of the liquid-crystal molecules in the PVH, the PVH mayfurther converge or diverge the incident light. In some examples, thePVH of the optical combiner may be also referred to as, a “polarizationsensitive grating,” a “polarization sensitive optical element,” a“liquid crystal grating,” or a “chiral liquid crystal element.” Whenconfigured as a PVH, the optical combiners 106 and 110 may include flator curved surfaces.

In some embodiments, optical combiner 106 may alternatively beconfigured as a “hot mirror”. When configured as a hot mirror, theoptical combiner 106 may include one or more reflecting layers thatreflect non-visible light (e.g., having the same wavelength as thenon-visible light 107) to the second camera 126 while passing visiblelight. The one or more hot mirrors may be in a line of sight of theuser, but since the hot mirrors pass visible light, external scene lightand/or display light will still propagate to the eye of the user.Therefore, in augmented reality (AR) implementations, a view of theexternal environment of the user is still viewable and in a virtualreality (VR) implementation, the user may view display light from avirtual reality display. In some examples, the hot mirror of opticalcombiner 106 may include a dichroic multi-layer optical film configuredto reflect non-visible light of a particular spectrum and to pass otherwavelengths of light, including visible light.

FIG. 1B illustrates an imaging optical path of the fundus imaging system100 for generating images of the eye 114 and of the fundus 112, inaccordance with aspects of the present disclosure. In some aspects, whenilluminated with non-visible light 107, each point on the fundus 112 ofeye 114 may operate as a point light source that reflects thenon-visible light 107 as reflected non-visible light 109. Furthermore,the reflected non-visible light 109 may exit the eye 114 nearlycollimated and as including multiple components (e.g., multiplepolarization orientations). In some examples, one component of thereflected non-visible light 109 is a polarization orientation that isthe same as the non-visible light 107 that was incident upon the fundus112.

As shown in FIG. 1B, the reflected non-visible light 109 is received atthe optical combiner 110. The optical combiner 110 may then direct afirst component 111 of the reflected non-visible light to the firstcamera 120, where the first camera 120 then generates one or images 123of the eye 114. FIG. 2A illustrates an example image 202A that may becaptured by first camera 120. In some examples, first camera 120 may beconfigured to filter out light that is other than the non-visible light107/reflected non-visible light 109 such that the first camera 120 onlyimages the wavelength of the reflected non-visible light 109.

FIG. 1B further illustrates the optical combiner 110 passing the secondcomponent 113 of the reflected non-visible light 109. In some examples,the first component 111 of the reflected non-visible light 109 is afirst polarization orientation (e.g., RCP), whereas the second component113 is a second polarization orientation (e.g., LCP) that is orthogonalto the first polarization orientation.

The second component 113 of the reflected non-visible light 109 thenpasses through the lens system 108, which then transmits a fundusimaging light 115 that is responsive to the second component 113. Forexample, in some aspects the lens system 108 may alter the polarizationorientation of the second component 113 of reflected non-visible lightinto a different polarization orientation and transmit the alteredsecond component as fundus imaging light 115. In yet another example,the lens system 108 may maintain the polarization state of the secondcomponent 113 as it propagates through the lens system as fundus imaginglight 115. In either case, when optical combiner 106 is implemented as aPVH, the PVH may be configured to reflect light of a particularpolarization orientation (and wavelength) that is the same as the fundusimaging light 115 received from the lens system 108. In some examples,the fundus imaging light 115 has the same wavelength as that of thereflected non-visible light 109. The optical combiner 106 receives anddirects the fundus imaging light 115 to the second camera 126, where thesecond camera 126 then generates one or images 127 of the fundus 112.FIG. 2B illustrates an example image 202B that may be captured by secondcamera 126. In some examples, the second camera 126 may be configured tofilter out light that is other than the reflected non-visible light 109such that the second camera 126 only images the wavelength of thereflected non-visible light 109.

In some examples, the fundus imaging system 100 may include aneye-tracking system to track movements of the eye 114. In theillustrated example, the eye-tracking system is provided by way of thefirst camera 120. The first camera 120 is communicatively coupled tocomputing device 122, which is configured to track movements of the eye114 based on the one or more images 123. In some examples, theeye-tracking system is a pupil-tracker that is configured to determinethe movements of the eye based on movements of the pupil 118.

In some examples, an eye-tracking module of the computing device 122 maybe configured to determine eye-tracking information (e.g., location,orientation, gaze angle, etc. of the eye 114). In some aspects, theeye-tracking module may be configured to receive an image 123 capturedby the first camera 120 and process the image to detect one or morespecular reflections. The eye-tracking module may then localize thedetected specular reflections to determine eye-tracking information(e.g., position, orientation, gaze angle, etc. of the eye 114). Forexample, the eye-tracking module may determine whether the eye 114 islooking in the straight, left, right, upwards, or downwards direction.

In some embodiments, the computing device 122 may include a controlmodule that is communicatively coupled to the array of light sources102A-102G. As shown in FIG. 1A, the eye 114 is generally looking forwardand is aligned with a center of the array of light sources 102A-102G.Thus, in this scenario a center light source (e.g., light source 102D)may be enabled to emit the non-visible light 107. However, as mentionedabove, if the eye 114 is not directly aligned, or if the eye 114 moves,the pupil 118 may vignette the non-visible light 107. Accordingly, thecontrol module of computing device 122 may generate one or more controlsignals 124 to selectively enable at least one of the light sources102A-102G based on the detected movements of the eye 114 to maintainillumination of the fundus 112.

For example, in some aspects, each light source 102A-102G of the arrayof light sources may include a corresponding position within the array.The control module may be configured to translate the detected movementsof the eye 114 to a position within the array to determine which of thelight sources 102A-102G to enable. In some embodiments, changing whichof the light sources 102A-102G is enabled changes an angle at which thenon-visible light 107 is emitted from the lens system 108. Thus, inoperation, the eye-tracking module of computing device 122 may detect amovement of eye 114 based on one or more of the images 123, where thecontrol module then translates the detected movements of the eye to aposition of a light source in the array of light sources.

FIG. 3 illustrates a computing device 302, in accordance with aspects ofthe present disclosure. The illustrated example of computing device 302is shown as including a communication interface 304, one or moreprocessors 306, hardware 308, and a memory 310. The computing device 302of FIG. 3 is one possible implementation of the computing device 122 ofFIG. 1A.

The communication interface 304 may include wireless and/or wiredcommunication components that enable the computing device 302 totransmit data to and receive data from other devices/components. Thehardware 308 may include additional hardware interface, datacommunication, or data storage hardware. For example, the hardwareinterfaces may include a data output device, and one or more data inputdevices.

The memory 310 may be implemented using computer-readable media, such ascomputer storage media. In some aspects, computer-readable media mayinclude volatile and/or non-volatile, removable and/or non-removablemedia implemented in any method or technology for storage of informationsuch as computer-readable instructions, data structures, programmodules, or other data. Computer-readable media includes, but is notlimited to, RAM, ROM, EEPROM, flash memory or other memory technology,CD-ROM, digital versatile disks (DVD), high-definition multimedia/datastorage disks, or other optical storage, magnetic cassettes, magnetictape, magnetic disk storage or other magnetic storage devices, or anyother non-transmission medium that can be used to store information foraccess by a computing device.

The processors 306 and the memory 310 of the computing device 302 mayimplement an eye-tracking module 312 and a fundus illumination sourcecontrol module 314. The eye-tracking module 312 and the fundusillumination source control module 314 may include routines, programinstructions, objects, and/or data structures that perform particulartasks or implement particular abstract data types. The memory 310 mayalso include a data store (not shown) that is used by the eye-trackingmodule 312 and/or fundus illumination source control module 314.

The eye-tracking module 312 may be configured to receive images (e.g.,images 123 of FIG. 1B) and process the images to determine a positionand/or movements of the eye 114. The eye-tracking module 312 may thencommunicate with the fundus illumination source control module 314 basedon the determined movements/position. The fundus illumination sourcecontrol module 314 may be configured to translate the eye movements to aposition within the array of light sources 102A-102G and generate one ormore control signals (e.g., control signals 124) to enable at least oneof the light sources 102A-102G to maintain illumination of the fundus112.

FIG. 4 is a flow chart illustrating a process 400 of imaging the fundusof an eye, in accordance with aspects of the present disclosure. Process400 includes one or more process blocks that may be performed by thecomputing device 122 of FIG. 1A and/or the computing device 302 of FIG.3.

Process block 402 includes capturing one or more images (e.g., images123 of FIG. 1B) of an eye (e.g., eye 114) with a first camera 120. In aprocess block 404, movements of the eye 114 are tracked. As discussedabove, the computing device 122 may analyzes the images 123 to determinethe position and/or movements of the eye 114. Next in a process block406, the computing device 122 selectively enables at least one lightsource of the array of light sources 102A-102G based on the movements ofthe eye. As discussed above, the enabling of a light source may includetranslating the movements of the eye 114 to a position within the arrayof light sources to maintain illumination of the fundus 112 withnon-visible light 107. Next, in process block 408, the second camera 126may capture one or more images of the fundus 112.

In some implementations, aspects of the present disclosure, such asfundus imaging system 100 of FIG. 1A, may be utilized in a head mounteddevice, such as a virtual reality (VR) or augmented reality (AR) device.In some aspects, a head mounted device may incorporate an eye-trackingsystem to enhance a user's viewing experience. Eye-tracking, may in someinstances, be aided by determining the position and/or movement of oneor more features present in the fundus of the eye. For example, a headmounted device may be configured to identify a fovea region from animage of the fundus and then determine a gaze angle of the eye based onthe identified fovea region. The fovea region may be determined usingone or more image processing techniques. When the gaze angle isdetermined, a virtual image presented to a user by a display of a headmounted device may be adjusted in response to the determined gaze angle.

By way of example, FIG. 5 illustrates a head-mounted display (HMD) 500,in accordance with aspects of the present disclosure. An HMD, such asHMD 500, is one type of head mounted device, typically worn on the headof a user to provide artificial reality content to a user. Artificialreality is a form of reality that has been adjusted in some mannerbefore presentation to the user, which may include, e.g., virtualreality (VR), augmented reality (AR), mixed reality (MR), hybridreality, or some combination and/or derivative thereof. The illustratedexample of HMD 500 is shown as including a viewing structure 540, a topsecuring structure 541, a side securing structure 542, a rear securingstructure 543, and a front rigid body 544. In some examples, the HMD 500is configured to be worn on a head of a user of the HMD 500, where thetop securing structure 541, side securing structure 542, and/or rearsecuring structure 543 may include a fabric strap including elastic aswell as one or more rigid structures (e.g., plastic) for securing theHMD 500 to the head of the user. HMD 500 may also optionally include oneor more earpieces 520 for delivering audio to the ear(s) of the user ofthe HMD 500.

The illustrated example of HMD 500 also includes an interface membrane518 for contacting a face of the user of the HMD 500, where theinterface membrane 518 functions to block out at least some ambientlight from reaching to the eyes of the user of the HMD 500.

Example HMD 500 may also include a chassis for supporting hardware ofthe viewing structure 540 of HMD 500 (chassis and hardware notexplicitly illustrated in FIG. 5). The hardware of viewing structure 540may include any of processing logic, wired and/or wireless datainterface for sending and receiving data, graphic processors, and one ormore memories for storing data and computer-executable instructions. Inone example, viewing structure 540 may be configured to receive wiredpower and/or may be configured to be powered by one or more batteries.In addition, viewing structure 540 may be configured to receive wiredand/or wireless data including video data.

Viewing structure 540 may include a display system having one or moreelectronic displays for directing light to the eye(s) of a user of HMD500. The display system may include one or more of a liquid crystaldisplay (LCD), an organic light emitting diode (OLED) display, amicro-LED display, etc. for emitting light (e.g., content, images,video, etc.) to a user of HMD 500. The viewing structure 540 may alsoinclude an optical assembly that is configured to receive the imagelight from the display system and generate a virtual image (e.g., bycollimating the image light) for viewing by an eye of a wearer of theHMD 500.

In some examples, viewing structure includes a fundus imaging system 545for obtaining one or more images of a fundus of the user's eye. Thefundus imaging system 545 may be implemented by way of any of theembodiments discussed herein, including fundus imaging system 100 ofFIG. 1A.

Embodiments of the invention may include or be implemented inconjunction with an artificial reality system. Artificial reality is aform of reality that has been adjusted in some manner beforepresentation to a user, which may include, e.g., a virtual reality (VR),an augmented reality (AR), a mixed reality (MR), a hybrid reality, orsome combination and/or derivatives thereof. Artificial reality contentmay include completely generated content or generated content combinedwith captured (e.g., real-world) content. The artificial reality contentmay include video, audio, haptic feedback, or some combination thereof,and any of which may be presented in a single channel or in multiplechannels (such as stereo video that produces a three-dimensional effectto the viewer). Additionally, in some embodiments, artificial realitymay also be associated with applications, products, accessories,services, or some combination thereof, that are used to, e.g., createcontent in an artificial reality and/or are otherwise used in (e.g.,perform activities in) an artificial reality. The artificial realitysystem that provides the artificial reality content may be implementedon various platforms, including a head-mounted display (HMD) connectedto a host computer system, a standalone HMD, a mobile device orcomputing system, or any other hardware platform capable of providingartificial reality content to one or more viewers.

The above description of illustrated embodiments of the invention,including what is described in the Abstract, is not intended to beexhaustive or to limit the invention to the precise forms disclosed.While specific embodiments of, and examples for, the invention aredescribed herein for illustrative purposes, various modifications arepossible within the scope of the invention, as those skilled in therelevant art will recognize.

These modifications can be made to the invention in light of the abovedetailed description. The terms used in the following claims should notbe construed to limit the invention to the specific embodimentsdisclosed in the specification. Rather, the scope of the invention is tobe determined entirely by the following claims, which are to beconstrued in accordance with established doctrines of claiminterpretation.

What is claimed is:
 1. A fundus imaging system, comprising: an array oflight sources configured to be selectively enabled to emit non-visiblelight to illuminate a fundus of an eye; a first optical combinerdisposed between the array of light sources and an eyeward side of thefundus imaging system, wherein the first optical combiner is configuredto: receive reflected non-visible light that is reflected by the eye,direct a first component of the reflected non-visible light to a firstcamera to generate an image of the eye, and pass a second component ofthe reflected non-visible light; and a second optical combiner disposedbetween the array of light sources and the first optical combiner,wherein the second optical combiner is configured to: receive a fundusimaging light responsive to the second component of the reflectednon-visible light, and direct the fundus imaging light to a secondcamera to generate an image of the fundus.
 2. The fundus imaging systemof claim 1, further comprising: a computing device configured todetermine movements of the eye based on the image of the eye and toselectively enable at least one light source of the array of lightsources based on the movements to maintain illumination of the fundus.3. The fundus imaging system of claim 1, wherein the non-visible lightcomprises infrared or near-infrared light.
 4. The fundus imaging systemof claim 1, further comprising: a lens system disposed between the firstoptical combiner and the second optical combiner, wherein the lenssystem is configured to direct the non-visible light emitted by at leastone light source of the array of light sources to illuminate the fundusof the eye.
 5. The fundus imaging system of claim 4, wherein the lenssystem is configured to focus the non-visible light to a pupil plane ofthe eye.
 6. The fundus imaging system of claim 1, wherein the firstcomponent of the reflected non-visible light is a first polarizationorientation, and wherein the second component of the reflectednon-visible light is a second polarization orientation that isorthogonal to the first polarization orientation.
 7. The fundus imagingsystem of claim 6, wherein the first optical combiner comprises a firstpolarized volume hologram configured to direct the reflected non-visiblelight of the first polarization orientation and to pass the reflectednon-visible light of the second polarization orientation.
 8. The fundusimaging system of claim 1, wherein the second optical combiner isconfigured to direct light to the second camera based on a wavelength ofthe fundus imaging light having a same wavelength as the non-visiblelight.
 9. The fundus imaging system of claim 8, wherein the secondoptical combiner comprises a second polarized volume hologram configuredto direct the fundus imaging light to the second camera based on apolarization orientation and the wavelength of the fundus imaging light.10. The fundus imaging system of claim 8, wherein the second opticalcombiner comprises a hot mirror that is configured to direct the fundusimaging light to the second camera based on the wavelength of the fundusimaging light.
 11. The fundus imaging system of claim 1, wherein thearray of light sources comprises a transparent substrate and whereineach light source of the array of light sources is disposed on thetransparent substrate.
 12. The fundus imaging system of claim 1, whereinthe first optical combiner and the second optical combiner aretransmissive to visible light.
 13. A head mounted display (HMD),comprising: a display layer configured to emit a display light forpresentation to a user; an array of light sources disposed on thedisplay layer and configured to be selectively enabled to emitnon-visible light to illuminate a fundus of an eye of the user; a firstoptical combiner disposed between the array of light sources and aneyeward side of the HMD, wherein the first optical combiner isconfigured to: receive reflected non-visible light that is reflected bythe eye, direct a first component of the reflected non-visible light toa first camera to generate an image of the eye, and pass a secondcomponent of the reflected non-visible light; and a second opticalcombiner disposed between the array of light sources and the firstoptical combiner, wherein the second optical combiner is configured to:receive a fundus imaging light responsive to the second component of thereflected non-visible light, and direct the fundus imaging light to asecond camera to generate an image of the fundus.
 14. The HMD of claim13, wherein the first component of the reflected non-visible light is afirst polarization orientation, and wherein the second component of thereflected non-visible light is a second polarization orientation that isorthogonal to the first polarization orientation.
 15. The HMD of claim14, wherein the first optical combiner comprises a first polarizedvolume hologram configured to direct the reflected non-visible light ofthe first polarization orientation and to pass the reflected non-visiblelight of the second polarization orientation.
 16. The HMD of claim 13,wherein the second optical combiner is configured to direct light to thesecond camera based on a wavelength of the fundus imaging light having asame wavelength as the non-visible light.
 17. The HMD of claim 16,wherein the second optical combiner comprises a second polarized volumehologram configured to direct the fundus imaging light to the secondcamera based on a polarization orientation and the wavelength of thefundus imaging light.
 18. The HMD of claim 16, wherein the secondoptical combiner comprises a hot mirror that is configured to direct thefundus imaging light to the second camera based on the wavelength of thefundus imaging light.
 19. The HMD of claim 13, wherein the first opticalcombiner and the second optical combiner are transmissive to the displaylight.
 20. A fundus imaging system, comprising: a first cameraconfigured to generate at least one image of an eye; a second cameraconfigured to generate at least one image of a fundus of the eye; anarray of light sources configured to be selectively enabled to emitnon-visible light to illuminate a fundus of an eye; a first opticalcombiner disposed between the array of light sources and an eyeward sideof the fundus imaging system, wherein the first optical combiner isconfigured to: receive reflected non-visible light that is reflected bythe eye, direct a first component of the reflected non-visible light tothe first camera to generate the at least one image of the eye, and passa second component of the reflected non-visible light; and a secondoptical combiner disposed between the array of light sources and thefirst optical combiner, wherein the second optical combiner isconfigured to: receive a fundus imaging light responsive to the secondcomponent of the reflected non-visible light, and direct the fundusimaging light to the second camera to generate the at least one image ofthe fundus.